<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    <script src="./js/vue.js"></script>
    <div id='app'>
       千米：<input type="number" v-model="km">
       米：<input type="number" v-model="m">
    </div>
    
    <script>
        let app =new Vue({
             el:"#app",
             data:{
                km:0,
                m:0
             },
             methods: {
                kmtom:function(val){
                    this.m=this.km*1000;
                },
                mtokm:function(val){
                    this.km=this.m/1000
                }
             },
             watch:{
                km:'kmtom',//监听数据km与m的变化，当其值发生变化，调用对应的方法
                m:'mtokm'//使用监听器会立即触发方法，而不像普通方法，需要有某些事件触发
             }
        })
    </script>
</body>
</html>